<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:xbl="http://www.mozilla.org/xbl">
<head>
  <style>
    .forced { display:block; }
  </style>
</head>
<body>
  <xbl:children>
    FAIL
  </xbl:children>

  <xbl:children class="forced">
    FAIL
  </xbl:children>

  <xbl:children />

  <script>
    var third = document.body.children[2];
    third.appendChild(document.createTextNode("FAIL"));

    var fourth = document.createElementNS("http://www.mozilla.org/xbl", "children");
    fourth.appendChild(document.createTextNode("FAIL"));
    document.body.appendChild(fourth);
  </script>
</body>
</html>
